Different areas of the intestinal tract have varying degrees of surgical accessibility. For example, there has been great difficulty in diagnosing and treating disorders in the human small intestine because of the length of the small intestine (typically about 21 feet or 7 meters), and its inaccessibility. Also certain regions of the colon have proven difficult to access for treatment. Accordingly, it would be desirable to provide a less or minimally invasive device for diagnosing or treating difficult to access portions of the intestinal tract, such as, the small intestine and colon.
Swallowable telemetry capsules have been used in a number of treatment and diagnostic applications. Some swallowable capsules have been proposed to deliver medication to specific areas of the intestinal tract where the release of the medication is actuated by an external RF signal received by the capsule. The signal actuates an electromechanical device within the capsule to release the medication. Similarly, some capsules have been proposed to acquire samples from the intestinal tract where actuation of an electromechanical sampling device is remotely controlled and the capsule is then retrieved when excreted. Other capsules have been proposed, for example, to take pictures or video images, or measure pH, pressure or temperature. An autonomous capsule with electrodes has been proposed to provide electrical stimulation while moving through the GI tract to restore motor evacutory function of the GI tract. Such a device has been proposed to propel a capsule through the gut.
Telemetry treatment and/or diagnostic capsules with mapping capabilities have been proposed to identify a target treatment site on a three-dimensional map of the intestinal tract. Generally, the proposed systems include capsules that transmit RF signals to externally located antennas. The relative amplitudes of the RF signals received by the antennas are used to determine relative location of the capsule based on the correlation between the capsule to antenna distance and RF amplitude (signal strength). According to these proposed systems, using four or more antennas and triangulation techniques, the location of the capsule in two or three-dimensional space is determined based on RF amplitude. From the location information, a map of the capsule's path in space may be created. In subsequent passes of the capsule through the intestinal tract, the capsule is used for treatment or diagnosis purposes at a target location. In addition, it has been proposed to use video images in combination with such RF determined spatial information to identify a target location in first and subsequent capsule passes.
A capsule with a mechanical cogwheel has been proposed to calculate the small bowel length and small bowel transit velocity. The device relies on the turning of the cogwheel by contact with the intestinal wall during small bowel transit to calculate centimeters of travel.
Many disadvantages are inherent in the current capsule tracking techniques. Tracking systems using RF amplitude data from signals transmitted through body tissue have a high degree of error and inadequate resolution for accurate intestinal tract mapping. (With 1 cm intestinal diameters and substantial overlap of intestines, an accurate resolution is necessary.) The resolution problems are due to a number of possible inaccuracies, which are compounded because RF signal strength over distance varies in a non-linear fashion. RF signal is directional, and thus its strength varies with the direction of the signal or the orientation of the coil transmitter with respect to the fixed coil receiver. Thus, without any change in location, a change in orientation may cause a dramatic change in RF amplitude at the antenna. Further, RF transmission is absorbed by tissue, particularly at higher frequencies. Thus the larger coils that would be required to transmit lower frequency RF signals, constrain the ability to miniaturize an optimal device.
In addition to RF resolution issues, due to movement and shifting of the intestinal organs within the abdomen, 3D mapping may not repeatably identify a precise location within the intestines when a subsequent capsule is passed through the tract. The intestinal organs tend to shift with the filling or emptying of the various portions of the digestive system, and they tend to move with peristalsis. A patient's abdomen also moves with respiration and change in patient position. Thus, given the intestinal shifting along with the intestine's small diameter and overlap, the 3D tracking system may identify the wrong portion of the intestinal tract when a later capsule passes through. Therefore, it would be desirable to provide a tracking system that accurately and repeatably identifies a desired location in the intestinal tract so that a location identified by a first capsule is substantially the same as a location identified by a subsequently passed capsule. It would also be desirable to provide a capsule and tracking system that does not rely on RF transmission amplitude data for accurate tracking.
As noted above, telemetry capsules have been used in therapeutic and diagnostic applications. Such therapeutic and diagnostic devices have typically involved providing medication to a location in the intestinal tract alone or in combination with sampling the fluids of the intestinal tract. The pH, temperature and pressure have also been measured. It would be desirable to provide capsules with new diagnostic and treatment modalities, particularly in a manner that would combine the treatment with tracking and diagnostic capabilities, to treat difficult to access regions of the intestinal tract.
One clinically significant condition that has been challenging to treat in the intestines is bleeding. Location of bleeding in the intestinal tract is very difficult to identify and requires surgical intervention to correct if it persists. Therefore, it would be desirable to provide a method and device for identifying a location of intestinal bleeding and for treating the location in a less invasive manner.
Another diagnostic/therapeutic area of interest is in identifying blockages or other diseased portions of the intestine and the ability to biopsy the specific location where there is such a blockage or disease. It would also be of interest to assist a surgeon in specifically marking a site for surgery prior to surgical intervention for easier identification of the site.
Another clinically significant parameter is the transit time of materials through the intestines. Current techniques in measuring transit time involve ingesting a material that reacts with the contents of the colon such that the patient's breath gives off a detectable gas at such time. This technique is not very precise and does not provide information on, e.g., which particular portion of the tract is responsible for transit abnormalities. Some patients have segmental diseases where a segment of the intestine does not have adequate motility. Thus, velocity of travel of materials through various portions of the intestine would be of interest in determining where there may be segmental disease.
Motility disorders in some situations relate to abnormalities in the periodic, coordinated contractile activity of the smooth muscles associated with the intestinal tract. Various organs of the intestinal tract such as the stomach, small intestine and colon contain cells that are believed to govern the organs' periodic contractile behavior. In healthy humans, in certain intestinal tract regions, these cells generate and propagate rhythmic electrical signals. In general, several types of electrical potential activities have been observed in the intestinal tract. Consistent slow wave or pacesetter potentials have been observed and higher frequency spike activity has been observed. The pacesetter potentials are continuously propagating, relatively low frequency, cyclic depolarizations of the smooth muscle lining. The higher frequency spike bursts tend to correspond with smooth muscle contractile activity including segmentation and peristalsis. In general, when the spike burst activity occurs, it appears to be at a fixed time delay with respect to the slow wave potentials. It is believed that when the pacesetter potentials are combined with a chemical or neural excitation of the cells, smooth muscle contractile activity may occur and that the pacesetter potentials control and coordinate the frequency and direction of the contractions.
Accordingly, it would be of interest to provide a means for observing the electrical activity such as, for example, the vagal nerve activity, the electromyogram, or of the intestinal smooth muscle layers, etc., to determine whether the electrical activity is abnormal, indicating possible disease.
Electrical stimulation of the gastrointestinal tract has been proposed to treat motility related disorders and other gastrointestinal diseases. The electrical stimulation has been proposed in a number of forms, such as, e.g., pacing; electrical contractile stimulation or other stimulation; e.g., to treat nausea. Electrical pacing of the intestinal tract is generally defined as periodic electrical stimulation that captures and/or controls the frequency of the pacesetter potential or slow wave activity of the intestinal organ (including in a retrograde direction). Electrical contractile stimulation generally refers to stimulation that directly causes or results in muscular contraction associated with the intestinal tract.
In some disease states, dysrhythmias of the intestinal tract pacesetter potentials may be present. Electrical pacing of pacesetter potentials has been proposed to induce regular rhythms for the pacesetter potentials with the intent of inducing regular or controlled intestinal tract contractions. Pacing has also been suggested to cause retrograde propagation of pacesetter potentials. Also, electrical contractile stimulation of the intestinal tract has been proposed to induce peristalsis.
Many currently proposed intestinal tract electrical stimulation procedures are relatively invasive and require accessing the intestinal tract through the abdomen, e.g., in an open or a laparoscopic procedure. The devices used typically require implanting permanent leads, electrodes and a pacemaker within the body. Therefore, it would be desirable to provide a less invasive device for electrically stimulating the intestinal tract, particularly in combination with a system for tracking the device and delivering the treatment to an identified location.